Japanese patent application no. 2001-147243 filed on May 17, 2001 is hereby incorporated by reference in its entirety.
The present invention relates to a press machine in which a drive mechanism and a slider are interconnected through a suspension mechanism.
FIG. 5 shows a press machine 1P in which a drive mechanism (e.g., crank mechanism 10) and a slider 5 are interconnected through a suspension mechanism 20P.
Referring to FIG. 5, the press machine 1P also comprises a crown 2, columns 3 and a bed 7. On the bed 7 is placed guides 8 each for slidably guiding a guide rod 6 connected to the slider 5.
The suspension mechanism 20P comprises a connecting rod 21 connected to a crank shaft 11, the top end of which forms the drive mechanism 10, a male screw member 23P rotatably connected to the bottom end of the connecting rod 21 through a pin 22, a female screw member 37P screwed over the male screw member 23P to form a slider positioning device 30P together with the male screw member 23P and a retainer 25P having a top end located within the cylindrical bottom of female screw member 37P and a bottom end integrally connected with the slider 5, the retainer also including a mounting member 26P integrally formed therewith.
The slider positioning device 30P comprises a motor 31P, a rotational-power transmission mechanism 32P including various gear wheels, a worm shaft and a worm wheel 35P. The worm wheel 35P is fixedly connected with the female screw member 37P through a key 36P for synchronous rotation.
As the motor 31P is rotatably started, the female screw member 37P may be rotated relative to the fixed male screw member 23P and moved up and down along the axis Z thereof. Thus, the vertical position of the slider 5 carried on the female screw member 37P may be regulated. Such a screw structure (or connection) is lubricated by oil which is gravity-supplied onto the periphery of the male screw member 23P through a longitudinal oil groove 23MZ formed thereon. After being lubricated, the oil is collected at the bottom end of the oil groove 23MZ for re-circulation.
When the drive mechanism 10 is started after the slider has been positioned, the connecting rod 21 is swingably moved to repeatedly move the male screw member 23P, female screw member 37P and retainer 25P (26P) up and down. Thus, the slider 5 may repeatedly be moved between the top and bottom dead centers.
The entire press machine including the suspension mechanism 20P and slider positioning device 30P is structured by combining (or assembling) a great number of components. The manufacturing precision for each component is limited due to various conditions (e.g., cost, technology and load capacity). Depending on the assembling operation, it is also limited to some degree to micrify a clearance for reducing a frictional resistance to provide a smooth action. On the other hand, there may be created a clearance larger than the above-mentioned limitation between adjacent components after they have been assembled.
On the contrary, there may be frequently a case that a relatively large clearance must positively be formed between adjacent components to eliminate any influence from possible heat shrinkage and deformation.
In any case, the presence of relatively large clearance between adjacent components degrades the mechanical precision in the press machine, reduce the precision (or quality) in the pressed products and produce vibration and noise during the pressing operation.
Furthermore, the power transmission capacity may be reduced by creating a power (load) imbalance from any spacing between adjacent components (e.g., between contacting faces or between pressure receiving faces). Additionally, the system in which the slider positioning device 30P is incorporated into the suspension mechanism 20P requires a complicated lubricating/cooling mechanism for the screw parts (23P and 37P) which form part of the slider positioning device 30P. This also causes contamination of the press machine due to the flow of lubricating (or cooling) oil drops.
Depending on the size of the clearance in the slider positioning device 30P (23P and 37P), the engagement between the screw parts (23P and 37P) maybe loosened during the pressing operation. In addition, the position (or die height) of the slider 5 may be changed to increase defectives and to degrade the yield.
The present invention may provide a press machine which may improve the mechanical precision and product precision (or quality) and greatly reduce vibration and noise by eliminating any backlash in the pressing power transmission.
In the press machine according to the present invention, the time period between the state in which the press stops and the other state in which a press load is produced after the press has been started is referred to as the xe2x80x9cnon-press load producing timexe2x80x9d. In the non-press load producing time, a first pressure layer is formed by charging a pressurized fluid into a first clearance between a first face, facing downward for example, (e.g., male screw member) of a first component selected from a plurality of components forming a suspension mechanism and a third face, facing upward for example, (e.g., female screw member) of a second component opposing the first face. Thus, a vertical clearance (or backlash) which is formed between the first and third faces apparently disappears. At the same time, the first and third faces are mechanically brought into direct contact with each other through the pressurized fluid.
At the same time, a second face (e.g., upward face) of the first component which is dynamically opposing the first face thereof is pressed against a fourth face (e.g., downward face) of the second component which is opposing to the second face, for example, under the action of an upward lifting force. Thus, a second clearance between the second and fourth faces disappears. Moreover, the second and fourth faces are brought into direct contact with each other so that no clearance (backlash) is formed therebetween.
Namely, a mechanical power-transmission connection is formed between the first component (e.g., male screw member) and the second component (e.g., female screw member) without backlash (or clearance). Thus, vibration and noise may greatly be reduced during a press startup process between a press start at which slider starts to move downward and a time whereat the press load start to be produced.
In a press load producing time in which the slider further moves downward to start the pressing operation and to continue the pressing operation, the upward drag force (or press load) from the second component (e.g., female screw member) increases. Thus, the internal pressure in the first pressure layer increases with the downward movement of the first component (e.g., male screw member) in the drive mechanism. Thus, a second pressure layer maybe formed and maintained in the second clearance between the second face (e.g., upward face) of the first component and the fourth face (e.g., downward face) of the second component using the pressure of the pressurized fluid increased when the press load exceeds the internal pressure of the first pressure layer. In other words, the second pressure layer is increased and maintained during the press load. Finally, the pressure in the second pressure layer is formed to be the same as the formed pressure of the first pressure layer in the non-press load producing time.
In other words, the second pressure layer is inversely formed while the thickness of the first pressure layer decreases. The thickness of the second pressure layer also increases. In such a process, vibration and noise may greatly be reduced.
As the first pressure layer subsequently disappears, the first and third faces are brought into direct contact with each other. Thus, the pressing power may be transmitted directly from the first component to the second component. In other words, the first and second components may be interconnected without loss in the transmission of pressing power.
As the slider moves upward after the pressing operation has been completed, the second pressure layer decreases and eventually disappears while the first pressure layer which is again formed and maintained, then increases.
Therefore, the present invention may provide a press machine which may improve the mechanical precision and pressing-product precision (or quality) and greatly reduce vibration and noise by eliminating any loss in the pressing power transmission.
The press machine according to the present invention may further comprise a slider positioning mechanism including a female screw member. This slider positioning device may adjust a position of the slider by rotating the female screw member. In this case, the suspension mechanism may include: a connecting rod having a top end connected to the drive mechanism; a male screw member having a top end pin-joined to a bottom end of the connecting rod, and a bottom end screwed in the female screw member; a retainer having a top end connected to the female screw member so as to move upward and downward with the female screw member; and a mounting member fixedly mounted between the retainer and the slider.
The mounting member may have a liquid-tight sealing member which liquid-tightly seals a lower portion of the female screw member and the retainer. The female screw member may have a downward face and an upward face dynamically opposing the downward face. The liquid-tight sealing member may have a first opposing face opposing the downward face of the female screw member. Moreover, the retainer may have a second opposing face opposing the upward face of the female screw member.
The relationship between the male screw member (or first component) and the female screw member (or second component) has previously been described. The similar relationship may be applied to the relationship among the female screw member, retainer and liquid-tight sealing member (mounting member).
In the relationship among the female screw member, the retainer and liquid-tight sealing member (mounting member), the first component may be the female screw member; the first face may be the downward face of the female screw member; and the second face may be the upward face of the female screw member. The second component may include the liquid-tight sealing member (mounting member) and the retainer, which are connected each other. The third face may be the first opposing face and the fourth face may be the second opposing face. The fluid may be charged into the first clearance between the downward face of the female screw member and the first opposing face of the liquid-tight sealing member, the second clearance between the upward face of the female screw member and the second opposing face of the retainer, and the passageway communicating between the first and second clearances.
In the non-press load producing time, a first pressure layer is formed by filling with the pressurized fluid between the downward face (or first face) of the female screw member (or first component) selected from the components forming the suspension mechanism and the first upward opposing face (or third face) of the mounting member (or second component) opposing the first face. As a result, a clearance (backlash) between the first and third faces apparently disappear while the first and second components are mechanically contacted (or connected) directly to each other through the pressurized fluid.
At the same time, the upward face (or second face) of the female screw member (or first component) dynamically opposing the downward face (or first face) of the same is pressed upward against the second downward opposing face (or fourth face) of the retainer (or second component) opposing the second face by the pressure (or upward lifting force) from the first face. Since the second face is thus brought into direct contact with the fourth face, no clearance (or backlash) is formed therebetween. Thus, the retainer receiving the entire weight of the slider may be supported by the female screw member.
In other words, the retainer and the mounting member (or second component) are mechanically connected to the female screw member (or first component) so as to mechanically transmit power without backlash (or clearance). Thus, vibration and noise may greatly be reduced during the press staring-up process, that is from a press start-up time in which the slider starts the downward movement to a time in which the press load starts to occur.
In the press load producing time in which the slider is further moved downward to initiate and continue the pressing operation, the upward drag force (or press load) from the slider increases. Thus, the internal pressure in the first pressure layer also increases as the female screw member (or first component) in the drive mechanism moves downward. Using the pressurized fluid increased by the fact that the press load exceeds the internal pressure of the first pressure layer, a second pressure layer may be formed and maintained in the second clearance between the female screw member (or first component) and the retainer (or second component). More specifically, the pressure of the second pressure layer is increased and maintained in the press load producing time. Eventually, the pressure in the second pressure layer is formed to be equal to the pressure of the first pressure layer produced in the non-press load producing time.
In other words, the second pressure layer is formed and maintained inversely as the thickness of the first pressure layer decreases. Subsequently, the thickness of the second pressure layer increases. During such process, vibration and noise ay greatly be reduced.
As the first pressure layer finally disappears, the downward face (or first face) of the female screw member (or first component) may be brought into direct contact with the first opposing face (or third face) of the mounting member (or liquid-tight sealing member: second component). Thus, the pressing power may be transmitted from the female screw member (or first component) directly to the mounting member (or second component). In other words, the mounting member (or second component) may be connected to the female screw member (or first component) without loss of press power transmission.
When the slider moves upward after completion of the pressing operation, the second pressure layer decreases and finally disappears while the first pressure layer is again formed and increased.